JP2000327957A - Metal corrosion inhibitor and metal corrosion inhibiting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a metal corrosion inhibitor capable of preparing a stable treating agent and forming anticorrosive film containing no toxic materials such as 6-valent chromic acid and having excellent corrosion resistance. SOLUTION: This metal corrosion inhibitor comprises one or more kinds of metal powders having a larger ionization tendency than the metal to be treated, a 6-valent chromic source, a reductive hydroxy organic compound, a stabilizer consisting of phosphoric acid and/or phosphate, a surfactant, a thickener, and an aqueous solvent. In this metal corrosion inhibitor, the dispersibility of the metal powder is good even in the presence of 6-valent chrome due to the stabilizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal anticorrosive for treating a surface of an iron-based metal such as steel, cast iron or the like, and a metal anticorrosion method using the metal anticorrosive.

[0002]

2. Description of the Related Art Conventionally, metal anticorrosives of this type include metal powders having a greater ionization tendency than the metal to be treated, such as zinc or aluminum powder when the metal to be treated is an iron-based metal, and hexavalent chromium. An aqueous solvent is provided which comprises an acid, a pH adjuster such as a metal oxide or a metal hydroxide, a reducing organic compound such as oxohydroxy low molecular ether, and an aqueous solvent.

When the metal anticorrosive is brought into contact with the surface of the metal to be treated and heated, the reducing organic compound reduces hexavalent chromium from a hexavalent chromium source to trivalent chromium and deposits on the surface of the metal to be treated. The metal powder is bonded and fixed to the metal surface using the trivalent chromium as an adhesive to form a metal anticorrosive film.

[0004]

In the above conventional metal corrosion inhibitor, the metal powder is added to the aqueous solvent containing the hexavalent chromium source, the pH adjuster, and the reducing organic compound. The treatment liquid is dispersed, but there is a problem in the stability of the treatment liquid because it contains hexavalent chromic acid, and the metal anticorrosive film after the heat treatment contains an organic substance. There is a problem that the surface hardness of the anticorrosion film is not sufficient and is easily damaged.

[0005]

According to the present invention, one or more kinds of metal powders having a greater ionization tendency than the metal to be treated, a hexavalent chromium source, A hydrophobic hydroxy organic compound and a stabilizer that is phosphoric acid and / or a phosphate, a surfactant,
A metal anticorrosive comprising a thickener and an aqueous solvent, and an aqueous solvent containing a hexavalent chromium source, a reducing hydroxy organic compound, a stabilizer, a surfactant, and a thickener in the metal anticorrosive. The metal powder is dispersed into a treatment liquid, and the treatment liquid is brought into contact with the surface of the metal to be treated, and heat-treated to reduce hexavalent chromium from the hexavalent chromium source contained in the metal anticorrosive. An object of the present invention is to provide a metal anticorrosion method of reducing to trivalent chromium by a hydroxy organic compound and depositing it on the surface of the metal to be treated, and bonding and fixing the metal powder to the surface of the metal to be treated using the trivalent chromium as an adhesive. .

[0006]

The treatment liquid contains phosphoric acid and / or phosphate as a stabilizer, and the phosphoric acid and / or phosphate may be contained in the treatment liquid containing hexavalent chromium, Stabilizes the dispersibility of When the reducing hydroxy organic compound reduces hexavalent chromium, it becomes an aldehyde which is easily volatilized, and is almost completely volatilized by heat treatment. Therefore, since organic substances are hardly detected in trivalent chromium deposited on the surface of the metal to be treated, the formed metal anticorrosive film has a high surface hardness and is less likely to be scratched. In addition, hexavalent chromium in the treatment liquid is almost completely reduced to trivalent chromium by the reducing hydroxy organic compound during the heat treatment, so that harmful hexavalent chromium is almost completely detected in the metal anticorrosive film. Not done.

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below. [Metal powder] The metal powder used in the present invention is a metal powder having a greater ionization tendency than the metal to be treated, and when the metal to be treated is, for example, an iron-based metal, zinc, aluminum, zinc-aluminum Powders such as alloys are used, and particularly preferred is a combination of zinc powder and aluminum powder. The metal powder preferably has a purity of 99.0% by weight or more, more preferably 99.5% by weight or more, The powder is desirably in the form of flakes.
And in the case of zinc, the thickness of the flake is 3 μm or less, the diameter is 10 μm or less, more preferably the thickness is 2 μm or less, and the diameter is 7 μm or less. In the case of aluminum, the thickness of the flake is 0.8 μmm or less. 10μ diameter
m or less, more preferably 0.5 μm or less in thickness and 7 μm or less in diameter.

The surface of the metal powder may be treated with a higher fatty acid, a higher aliphatic alcohol, a high melting point wax, a high melting point paraffin or the like. To treat the surface of the metal powder with these fatty acids, alcohols, waxes, and paraffins, these fatty acids, alcohols, waxes, and paraffins are dissolved in kerosene, mineral spirit, mineral turpentine, and the like, and the metal powder is added to the solution. Dipping or spray mixing the solution with the metal powder.

When the metal powder is zinc, when the surface is treated with these fatty acids, alcohols, waxes and paraffin, the surface of the zinc powder reacts with hexavalent chromic acid in the metal anticorrosive to form zinc chromate, Further, it reacts with phosphoric acid and / or phosphate in the metal anticorrosive agent to form zinc phosphate, thereby imparting desirable anticorrosion properties. When zinc and aluminum are used together as the metal powder, zinc powder having a smaller ionization tendency than aluminum is disposed in the lower layer by such a surface treatment, and the aluminum powder is easily disposed in the upper layer, so that a desirable anticorrosion property is obtained. Granted.

The above metal powder is usually added to the metal anticorrosive of the present invention in an amount of 2 to 75% by weight, preferably 5 to 40% by weight, and when zinc powder and aluminum powder are used in combination,
The addition amount of zinc powder is 1 to 30% by weight, preferably 5 to 2%.
The addition amount of aluminum powder is set in the range of 1 to 25% by weight, preferably 3 to 15% by weight.

[Hexavalent chromium source] The compound used as a hexavalent chromium source in the present invention is mainly hexavalent chromic acid, that is, chromic anhydride, but hexavalent chromate such as potassium dichromate is also used. Can be used. Further, it is preferable that a small amount of trivalent chromic acid is mixed in the hexavalent chromic acid, and when heated on the surface of the metal to be treated due to the presence of trivalent chromic acid,
Hexavalent chromium is smoothly reduced to trivalent chromium by the reducing agent, and adheres the coexisting metal powder to the metal surface.

In preparing the treatment solution of the metal anticorrosive of the present invention, the hexavalent chromic acid is dissolved in water, preferably in distilled water or deionized water. The addition amount of hexavalent chromic acid in the metal anticorrosive of the present invention is 1 to 35% by weight, preferably 2 to 15% by weight as a solid content.

[Reducing hydroxy organic compound] In the present invention, a reducing hydroxy organic compound is used as a reducing agent. The reducing agent is easily oxidized near the processing temperature, that is, the temperature at which hexavalent chromic acid starts to melt and decompose, and exhibits a reducing action on hexavalent chromium, but is an organic compound which is stable at room temperature and does not reduce hexavalent chromic acid. However, by using such a reducing agent, the hardness of the metal anticorrosive film formed by the metal anticorrosive agent of the present invention is prevented from being lowered.

Examples of the reducing hydroxy organic compound include ethylene glycol, diethylene glycol, propylene glycol, glycerin, dipropylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol, methoxypropylene. Examples include glycol, ethoxypropylene glycol, butoxypropylene glycol, methoxydipropylene glycol, ethoxydipropylene glycol, butoxydipropylene glycol, and polyethylene / polypropylene glycol polymers. Preferred among the reducing hydroxy organic compounds are propylene glycol, dipropylene glycol, methoxypropylene glycol, methoxydipropylene glycol, ethoxydipropylene glycol, and glycerin. The amount of the reducing hydroxy organic compound to be added is 0.02 to 5 mol in terms of a molar ratio with respect to the amount of hexavalent chromic acid used, and a more desirable molar ratio is 0.05 to 2 mol.

[Stabilizer] In order to obtain a good metal anticorrosive film, it is necessary to hold the metal powder and hexavalent chromic acid in the metal anticorrosive agent at a constant film pressure on the surface of the metal to be treated. .
For this purpose, it is necessary to improve the dispersibility of the metal powder in the treatment liquid, and a surfactant or a thickener is usually used. However, the oxidizing power of the coexisting hexavalent chromic acid inhibits the dispersion stability of the metal powder.

Accordingly, in the present invention, phosphoric acid and / or phosphate is added as a stabilizer. Examples of the phosphoric acid and / or phosphate include phosphoric acid, sodium phosphate monobasic, sodium phosphate dibasic, sodium phosphate tertiary, potassium phosphate monobasic, potassium phosphate dibasic, and tertiary phosphate. Potassium, dibasic magnesium phosphate, tribasic magnesium phosphate, dibasic zinc phosphate, tribasic zinc phosphate, iron phosphate, nickel phosphate, copper phosphate and the like can be mentioned. Particularly preferred stabilizers include dibasic magnesium phosphate, tribasic magnesium phosphate, dibasic zinc phosphate, tribasic zinc phosphate, nickel phosphate and copper phosphate. The amount of the stabilizer is 0.1 to 15% by weight, more preferably 0.3 to 5% by weight.
It is.

[Surfactant] In the metal anticorrosive of the present invention, a surfactant is added in order to disperse the metal powder well in the treatment liquid. Examples of the surfactant include an alkylallyl ether type nonionic surfactant such as polyoxyethylene nonylphenyl ether and polyoxyethylene octylphenyl ether, polyoxyethylene butyl ether, and polyoxyethylene octyl.
Alkyl ether type nonionic activators such as ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene laurate, polyoxyethylene oleate, polyoxyethylene stearate And the like, and an alkyl ester type non-ionic activator such as polypropylene glycol / polyethylene glycol ether and the like.
H. of these nonionic surfactants L. B. (Hydoro
Non-ionic surfactants having a file-lipophilic balance of 7 or more and 18 or less are preferred as the surfactant used in the present invention, and H.P. L. B. Is in the range of 11 to 14. The addition amount of the surfactant is 0.05 to 8% by weight, preferably 0.1 to 5% by weight.

[Aqueous Solvent] As described above, hexavalent chromic acid is provided as an aqueous solution in the metal anticorrosive treating solution of the present invention. To improve dispersion, a water-soluble organic solvent is further added as a solvent. Examples of the water-soluble organic solvent include 1-propanol, 2-propanol, primary butanol, secondary butanol, tertiary butanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, butyl cellosolve,
Methyl carbitol, ethyl carbitol, butyl carbitol, butylene glycol, 2-ethyl-1,3-
Hexanediol, neopentyl glycol, 1,5-
Pentanediol, 2,3-dimethyl-2,2-butanediol, diacetone alcohol and the like. More preferred water-soluble organic solvents include glycerin, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, dipropylene glycol, 2-ethyl-1,3-hexanediol, 1,5-
There is pentanediol, and the amount of the water-soluble organic solvent to be added is usually 3 to 40% by weight, preferably 8 to 35% by weight.

[Thickener] In the metal anticorrosive of the present invention, a thickener must be added in order to ensure the thickness of the coating layer of the treatment liquid on the surface of the metal to be treated. Examples of the thickener used in the present invention include methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, ethylcellulose, carboxyethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, starch, nonionic starch, pectin, guar gum, tamarind gum, roast bean. Water-soluble thickeners such as gum, galactomannan, carrageenan, agar and the like can be mentioned. More preferred thickeners are carboxymethyl cellulose, hydroxymethyl cellulose and hydroxyethyl cellulose. The amount of the thickener added is 0.05
-5% by weight, preferably 0.1-1% by weight.

[Treatment method] In the metal anticorrosive of the present invention, when used, the above hexavalent chromic acid aqueous solution, reducing hydroxy organic compound, phosphoric acid and / or phosphate, surfactant, thickener, and water A treatment liquid is prepared by mixing a neutral organic solvent and dispersing the metal powder, and the viscosity of the treatment liquid is usually adjusted within 50 ± 10 seconds using an Iwata-type Ford cup # 4. In order to treat the surface of a metal to be treated with the treatment liquid, the surface of the metal is first polished by shot blasting, sand blasting or the like, and if necessary, trichlorethylene, perchlorethylene, benzene, toluene,
After washing with an organic solvent such as xylene and drying, the above treatment liquid is applied to the metal surface by dipping, spraying, roll coater, curtain flow coater, rotating brush coater, electrostatic coating or the like. After the treatment liquid is applied, the substrate is left at room temperature, dried by blowing air if necessary, and subjected to a preheating treatment at 150 to 160 ° C. for at least 10 minutes, followed by 300 ± 10 ° C.
Heat treatment at a temperature of at least 20 minutes. By the heat treatment, the organic substance originating from the metal anticorrosive of the present invention is almost completely decomposed and volatilized on the metal surface, and hexavalent chromium is almost completely reduced to trivalent chromium. An anticorrosive film is formed with trivalent chromic acid in which chromium is not detected as an adhesive. The anticorrosion film may be further coated with a paint if desired.

[0021]

EXAMPLES [Example 1] The following materials were sufficiently stirred and mixed. Aluminum paste * ¹ 8.0 parts by weight Zinc powder * ² 8.0 亜 鉛 Zinc diphosphate 1.0 〃Glycerin 2.5 〃Diethylene glycol 21.0 ポ リ Polyoxyethylene octyl alcohol ether * ³ 0.5 〃 * ¹ : Aluminum powder (thickness: 0.5 μm, diameter: 10.0 μm) is put into a mineral spirit solution containing 10% of stearyl alcohol, mixed well, and subjected to compression filtration. The evaporation residue was 68.5%. * ² : Zinc powder was produced by the atomization method, then made into flakes, and treated with higher aliphatic alcohol. The flake thickness was 1.0 μm and the length was 0.5 to 10 μm. * ³ : Polyoxyethylene octyl alcohol ether is H.E. L. B. 1 1.8 was used.

To the above mixture, 59 parts by weight of aqueous chromic acid (an aqueous solution of 8% by weight of chromic anhydride) is added, and while mixing and stirring, 0.4 parts by weight of hydroxyethyl cellulose is added and stirred. After stirring for 30 hours or longer, the viscosity of the obtained mixed solution was measured with an Iwata-type Ford cup # 4, and it was 51 seconds. Then, the mixture was filtered through a 100-mesh sieve to obtain a treatment liquid A.
And

Example 2 The following formulation was mixed in the same manner as in Example 1. Aluminum paste * ⁴ 10.0 parts by weight Zinc powder (identical to Example 1) 12.0 {magnesium diphosphate 3.0} dipropylene glycol 7.0 {diethylene glycol 7.0} polyoxyethylene nonylphenol ether * ⁵ 1.0 Chromic acid water (7.0% by weight) 60.0 Hydroxyethyl cellulose 0.3 〃 * ⁴ : Aluminum powder (thickness: 0.25 μm, diameter: 7.0 μm) mainly composed of stearyl alcohol The mixture is mixed well in a mineral turpentine containing 15% by weight of the prepared higher aliphatic alcohol, and then subjected to compression filtration. The evaporation residue is 69% by weight. * ⁵ : Polyoxyethylene nonylphenol ether is H.E. L. B. 12. Three were used. The viscosity of the mixture was 48 seconds with an Iwata-type Ford cup # 4. The mixture is filtered through a 100-mesh sieve to obtain a treatment liquid B.

Example 3 The following formulation was mixed in the same manner as in Examples 1 and 2. 8.0 parts by weight of aluminum paste * ⁶ Zinc powder (same as in Example 1) 11.0 {Zinc triphosphate 4.0} Glycerin 6.8 {Diethylene glycol 15.0} Polyoxyethylene lauryl ether * ⁷⁰ . 2 Chromic acid water (9.0% by weight) 55.0 {Hydroxyethyl cellulose 0.5} * ⁶ : Wax (melting point: 57 ° C) aluminum powder (thickness: 0.25 µm, diameter: 7.0 µm) Mix well in kerosene containing 10% by weight and filter by compression. The evaporation residue is 65% by weight. * ⁷ : Polyoxyethylene lauryl ether is H.E. L. B. 12.8 was used. The mixed solution was filtered in the same manner as in Examples 1 and 2 to obtain a treatment liquid C. The viscosity of the treatment liquid is 60 seconds. .

Example 4 The following formulation was used in Examples 1, 2, 3
Mix as above. Aluminum paste (same as in Example 1) 7.0 parts by weight Zinc powder (same as in Example 1) 10.0 {magnesium diphosphate 2.5} glycerin 4.0 {diethylene glycol 17.1} polyoxyethylene lauryl Ether (identical to Example 3) 0.4 {Chromic acid water (8.0% by weight) 59.0} Hydroxyethyl cellulose 0.4 {Filtering the above mixture in the same manner as in Examples 1, 2, and 3 The treatment liquid D was used. The viscosity of the treatment liquid D is 53 seconds. .

[Test] 1. Sample (1) Steel plate: SS-41 steel plate (50 × 100 × 0.5 mm)
It was used. The steel plate was polished on its surface by shot blasting, then washed with trichlorethylene and dried. (2) Screw: length 75mm, diameter 2mm, head 8mm, screw part 50
mm Phillips screws were used.

2. Coating (1) Steel plate Each of the above-mentioned treatment liquids A, B, C, and D is applied to the above steel plate at a thickness of 20 μm.
m, air-dried for 1 minute, put in a dryer at 150 to 160 ° C, preheated and dried for 10 minutes, and then
Heat treatment was performed at 20 ° C. for 20 minutes. (2) Screws The screws are immersed in each of the treatment liquids A, B, C, and D,
After pulling up, dewatering is performed for 1 minute by a dehydrator, air-dried for 1 minute, and then preheated and dried at 150 to 160 ° C for 10 minutes, and then heat-treated at 300 ± 10 ° C for 20 minutes. This process was repeated twice.

[Test Results] 1. Adhesion of the coating film (1) Inspection method The head of the “screw” treated with the above-mentioned treatment liquids A, B, C, D is strongly pressed against the palm. Examine the palm for any deposits. (2) Results When each of the "screw" treated with the above-mentioned treatment liquids A, B, C, and D was inspected five by five, it was found that no adhesion was observed in any case and good adhesion was exhibited.

2. Salt Spray Test A salt water spray test was performed on the steel plate and the screw according to JIS-Z-23717. Table 1 shows the results.

[Table 1] ^* Treatment solution E is a normal zinc plating. A similar steel plate was subjected to zinc plating with a film thickness of about 20 μm using the zinc plating solution, and a colored chromate treatment was performed. Evaluation ○: No change, Δ: Slight rust, ×: Rust on the whole surface △ 1: Slight rust on one of five screws △ 2: Slight rust on two of five screws ×: on five of screws All 5 rusted [Steel was cut in the cloth. One set of five screws was used. According to Table 1, treatment liquids A, B,
The samples treated with C and D all had excellent corrosion resistance, but the samples treated with the conventional galvanizing solution E showed much lower corrosion resistance than the sample of the present invention.

3. Weather resistance test Each of the above steel sheets was placed at an angle of 45 ° on the south side in Joyo City, Kyoto Prefecture.
Then, it was left for 30 days to perform a weather resistance test. Table 2 shows the results.

[Table 2] Evaluation ：: No change According to Table 2, the treatment solution A with the metal anticorrosive of the present invention,
B, C, and D were all shown to have excellent weather resistance.

4. Detection of Hexavalent Chromic Acid Ten "screw" treated each with the above-mentioned treatment solutions A, B, C and D with the metal anticorrosive of the present invention are immersed in 100 ml of distilled water, and after 48 hours, A diphenylcarbazide solution was added to generate a red-purple complex salt, and the absorbance was determined at a wavelength of 540 mμ. Neither solution developed color and the absorbance was 6
No chromic acid was detected. Therefore, 6
It was shown that no valent chromic acid was included.

[0032]

Accordingly, in the metal anticorrosive of the present invention, a stable treatment liquid is provided, and a corrosion resistant film having excellent corrosion resistance which does not contain harmful substances such as hexavalent chromium is formed on the metal surface. Can be done.

Claims (2)

[Claims] 1. A metal powder having a higher ionization tendency than a metal to be treated, one or more metal powders, a hexavalent chromium source, a reducing hydroxy organic compound and a stabilizer which is phosphoric acid and / or phosphate. A metal anticorrosive, comprising a surfactant, a thickener, and an aqueous solvent 2. The metal anticorrosive according to claim 1, wherein said metal powder is dispersed in an aqueous solvent containing a hexavalent chromium source, a reducing hydroxy organic compound, a stabilizer, a surfactant and a thickener. The treatment liquid is brought into contact with the surface of the metal to be treated, and then heat-treated to convert hexavalent chromium from the hexavalent chromium source contained in the metal anticorrosive into trivalent chromium with a reducing hydroxy organic compound. A method of reducing the amount of chromium and depositing it on the surface of the metal to be treated, and bonding and fixing the metal powder to the surface of the metal to be treated using the trivalent chromium as an adhesive.